Move some logic into Whateverable::Bisection

Also some refactoring in Bisectable.

META6.json

@@ -1,7 +1,7 @@
 {
     "perl"        : "6.c",
     "name"        : "Whateverable",
-    "version"     : "1.0.1",
+    "version"     : "1.0.2",
     "description" : "Different IRC bots that operate on a bunch of prebuilt Rakudo versions",
     "authors"     : [
         "Aleks-Daniel Jakimenko-Aleksejev <alex.jakimenko@gmail.com>",
@@ -10,6 +10,7 @@
     "license"     : "AGPL-3.0-or-later",
     "provides"    : {
         "Whateverable"               : "lib/Whateverable.pm6",
+        "Whateverable::Bisection"    : "lib/Whateverable/Bisection.pm6",
         "Whateverable::Bits"         : "lib/Whateverable/Bits.pm6",
         "Whateverable::Builds"       : "lib/Whateverable/Builds.pm6",
         "Whateverable::Config"       : "lib/Whateverable/Config.pm6",

lib/Whateverable/Bisection.pm6

@@ -0,0 +1,154 @@
+# Copyright © 2016-2018
+#     Aleks-Daniel Jakimenko-Aleksejev <alex.jakimenko@gmail.com>
+# Copyright © 2016
+#     Daniel Green <ddgreen@gmail.com>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+use Whateverable::Bits;
+use Whateverable::Builds;
+use Whateverable::Config;
+use Whateverable::Output;
+use Whateverable::Running;
+
+unit module Whateverable::Bisection;
+
+enum RevisionType is export <Old New Skip>;
+
+#↓ Use this to bisect stuff across a bunch of builds
+#↓ It can be used to bisect anything (not just Rakudo), it
+#↓ all depends on what you provide in &runner and :$repo-cwd.
+sub run-bisect(&runner  = &standard-runner,  #← Something to run on every revision
+               &decider = &adaptive-decider, #← Something to classify the result from &runner
+               :$skip-missing-builds = True, #← True to Skip if not build-exists
+               :$repo-cwd,                   #← Repo path where we will run `git bisect`
+               *%custom,                     #← Anything that may be needed in &runner or &decider
+              ) is export {
+    my $status;
+    my $first-new-commit;
+
+    my @bisect-log = gather loop {
+        NEXT take “»»»»» {‘-’ x 73}”; # looks a bit nicer this way
+        my $current-commit =  get-output(cwd => $repo-cwd,
+                                         <git rev-parse HEAD>)<output>;
+        take “»»»»» Testing $current-commit”;
+
+        if $skip-missing-builds and not build-exists $current-commit {
+            take ‘»»»»» Build does not exist, skip this commit’;
+            return Skip # skip non-existent builds
+        }
+
+        my $run-result     = &runner(              :$current-commit, |%custom);
+        my $revision-type  = &decider($run-result, :$current-commit, |%custom);
+        my $result         = get-output cwd => $repo-cwd,
+                                        <git bisect>, $revision-type.lc;
+        $status = $result<exit-code>;
+        if $result<output> ~~ /^^ (\S+) ‘ is the first new commit’ / {
+            $first-new-commit = ~$0;
+            last
+        }
+        last if $status ≠ 0;
+        LAST take $result<output>
+    }
+    my $log = @bisect-log.join(“\n”);
+    %( :$log, :$status, :$first-new-commit )
+}
+
+#↓ Runs a file containing a code snippet. Needs :$code-file custom arg.
+sub standard-runner(:$current-commit!, :$code-file!, *%_) is export {
+    run-snippet $current-commit, $code-file
+}
+
+#↓ Takes an output of run-snippet or get-output and uses it to decide
+#↓ what to do. You must provide exactly one named
+#↓ argument ($old-exit-code, $old-exit-signal, $old-output).
+#↓ Generally it considers any deviation from $old-* to be the New
+#↓ behavior, so effectively it finds the first change. Whether
+#↓ that change is good or not is left for user discretion, here we
+#↓ just work with Old / New / Skip concepts.
+sub adaptive-decider($result,
+                     :$current-commit,
+                     :$old-exit-code,
+                     :$old-exit-signal,
+                     :$old-output,
+                     *%_) is export {
+
+    if $result<exit-code> < 0 { # TODO use something different. … like what?
+        take “»»»»» Cannot test this commit. Reason: $result<output>”;
+        take ‘»»»»» Therefore, skipping this revision’;
+        return Skip # skip failed builds
+    }
+
+    take ‘»»»»» Script output:’;
+    my $short-output = shorten $result<output>, $CONFIG<bisectable><trim-chars>;
+    take $short-output;
+    if $short-output ne $result<output> {
+        take “»»»»» (output was trimmed  because it is too large)”
+    }
+
+    take “»»»»» Script exit code: $result<exit-code>”;
+    take “»»»»» Script exit signal: {signal-to-text $result<signal>}”
+        if $result<signal>;
+
+    if $result<exit-code> == 125 {
+        take ‘»»»»» Exit code 125 means “skip”’;
+        take ‘Therefore, skipping this revision as you requested’;
+        return Skip # somebody did “exit 125” in their code on purpose
+    }
+
+    # compare signals
+    with $old-exit-signal {
+        take ‘»»»»» Bisecting by exit signal’;
+        take “»»»»» Current exit signal is {signal-to-text $result<signal>},”
+          ~ “ exit signal on “old” revision is {signal-to-text $old-exit-signal}”;
+        if $old-exit-signal ≠ 0 {
+            take “»»»»» Note that on “old” revision exit signal is normally”
+              ~ “ {signal-to-text 0}, you are probably trying”
+              ~ “ to find when something was fixed”
+        }
+        take ‘»»»»» If exit signal is not the same as on “old” revision,’
+          ~ ‘ this revision will be marked as “new”’;
+        my $revision-type = $result<signal> == $old-exit-signal ?? Old !! New;
+        take “»»»»» Therefore, marking this revision as “{$revision-type.lc}””;
+        return $revision-type
+    }
+
+    # compare exit code (typically like a normal ｢git bisect run …｣)
+    with $old-exit-code {
+        take ‘»»»»» Bisecting by exit code’;
+        take “»»»»» Current exit code is $result<exit-code>, ”
+        ~ “exit code on “old” revision is $old-exit-code”;
+        if $old-exit-code ≠ 0 {
+            take ‘»»»»» Note that on “old” revision exit code is normally 0,’
+            ~ ‘ you are probably trying to find when something was fixed’
+        }
+        take ‘»»»»» If exit code is not the same as on “old” revision,’
+        ~ ‘ this revision will be marked as “new”’;
+        my $revision-type = $result<exit-code> == $old-exit-code ?? Old !! New;
+        take “»»»»» Therefore, marking this revision as “{$revision-type.lc}””;
+        return $revision-type
+    }
+
+    # compare the output
+    with $old-output {
+        take ‘»»»»» Bisecting by output’;
+        take ‘»»»»» Output on “old” revision is:’;
+        take $old-output;
+        my $revision-type = $result<output> eq $old-output ?? Old !! New;
+        take “»»»»» The output is {$revision-type == Old
+                                   ?? ‘identical’ !! ‘different’}”;
+        take “»»»»» Therefore, marking this revision as “{$revision-type.lc}””;
+        return $revision-type
+    }
+}